The invention relates to a feeding and discharging apparatus for an installation under subatmospheric pressure, which enables particulate material, e.g. in the form of grains or powder, to pass continuously through the installation.
When an installation for the treatment of a solid material, in the form of grains or powder, is intended to operate under vacuum, it is very difficult to continuously feed the installation with material to be treated, and to discharge the material resulting from the treatment, it not being possible for the material to be supplied directly under leaktight conditions from the outside into the installation under vacuum, and from the installation under vacuum to the outside.
In particular, a vacuum jet mill is known, the performance of which is very superior to that of conventional mills which can be used for grinding clinker, and which has not hitherto been employed industrially for various reasons, inter alia because it was not possible to ensure the continuous operation of the mill for long periods.
One of the major difficulties in ensuring the continuous operation of the jet mill lies in its feeding with the material to be ground and in the discharging of the ground material, which operations must be carried out into and out of an enclosure under vacuum. Solely discontinuous systems have therefore been used hitherto, the material being stored in a buffer compartment at the start of the operation and collected in another buffer compartment during the operation, these compartments being situated inside the enclosure under vacuum. This method of operation obviously prohibits the industrial use of the vacuum mill.